Wind power is generally considered the fastest growing energy source worldwide. The long-term economic competitiveness of wind power as compared to other energy production technologies has challenged members of the wind power industry to reduce wind power energy costs. One issue for concern for wind turbine operators is damage due to fatigue loads caused by fluctuating wind conditions. Assessing fatigue loads is important in the wind energy generation industry because fatigue load data can be used to verify designs are not over-engineered.
Fatigue loads can also be monitored to determine performance in various environments and in various conditions. Knowledge of fatigue loads can also be beneficial to the operator because the operating conditions and service life of a wind turbine may be adjusted by the operator to improve profit margins.
For example, by knowing the cumulative equivalent fatigue damage level of the turbine components, the operator may safely run the turbine beyond the design life and thus extend the service life because the service life becomes based on the measured cumulative equivalent fatigue damage levels instead of a theoretically derived cumulative equivalent fatigue damage used to predict a chronological design life based on wind data. For another example, in low wind seasons or low wind years where reduced fatigue damage occurs, the operator may increase the aggressiveness of turbine operation to work harder and accumulate more fatigue cycles while capturing more energy during the wind events. In this example, controlling the turbine operating aggressiveness level based on cumulative equivalent fatigue damage levels allows the operator to capture more energy and more profit on newly installed turbines. Thus the operator may benefit by matching turbine performance to achieve economic models based on cumulative equivalent fatigue damage levels. (e.g. Increased revenues can be generated while the turbine is new to benefit time-value-of-money models).
Currently, fatigue loads are generally measured using sensors such as bonded or welded strain gauges that require expertise to install and maintain and have only a limited life cycle of 6 to 24 months. Thus, current fatigue monitoring techniques are complex, costly and unreliable for long life applications.